This invention relates generally to lighting control systems and, more particularly, to lighting control systems that include separate plug-in dimmer modules for each of a plurality of lighting fixtures.
Lighting control systems of this particular kind are commonly used in theater, television and architectural lighting applications. The systems typically provide controlled amounts of electrical power to each of a large number of lighting fixtures that project beams of light onto a stage or other selected area. Each dimmer module is associated with one or two lighting fixtures or groups of lighting fixtures, for controlling the amount of electrical power supplied to each fixture or group of fixtures. These modules typically are housed in a rack that is either stand-up, wall-mounted or portable, and a central controller supplies to each module a separate pulse-width modulated control signal whose pulse width controls the amount of electrical power to be supplied to each fixture or group of fixtures.
An exemplary dimmer module of the kind referred to above is disclosed in U.S. Pat. No. 4,972,125 to Cunningham et al., entitled "Plug-In Dimmer Module for Lighting Control Systems." The module includes a generally rectangular plastic housing with plug-in electrical contacts on its rearside for carrying input power, output power to the load (i.e., an associated lighting fixture), and control signals. The module depicted in the patent provides electrical power to two separate lighting fixtures or groups of fixtures. Each module includes two circuit breakers, an electronic power device for switching power to the two loads, and two toroidal chokes, one for each load. The power device includes silicon-controlled rectifiers (SCRs) for supplying controlled amounts of electrical current through the chokes to the loads in accordance with pulse-width modulated control signals supplied to the module by the central controller. The power device further includes a built-in heat sink for dissipating heat generated by the SCRs.
All external connections to the dimmer module are made via plug-in electrical contacts located on the housing's rear side such that the module conveniently can be slid into a rack to complete the connections. In particular, a single input power contact is located at one end of the housing's rear side, for delivering ac electrical power to the two circuit breakers, which are stacked one above the other at that end of the housing. Immediately adjacent to the input power contact are a number of control signal contacts which deliver control signals via separate conductors to the power device. The power device is located in a middle section of the housing, and it includes lead frames that plug directly into the circuit breakers. The toroidal chokes, which are arranged side-by-side at the end of the dimmer module's housing opposite the circuit breakers, receive controllably-switched electrical power from the power device via flat electrical leads that extend around the power device's heat sink. The chokes in turn supply the controllably-switched power to separate output contacts located at the end of the housing's rear side opposite the input contact.
The layout of components for the dimmer module described above is a logical, generally efficient arrangement; however, it is not believed to be as efficient as is possible. First, the positioning of the plug-in contacts for the control signals relative to the positioning of the power device requires the use of separate conductors for carrying the signals from one to the other. Second, the positioning of the power device in a middle section of the dimmer module's housing requires the use of separate conductors for carrying the controllably-switched electrical power around the heat sink to the toroidal chokes. These additional conductors are believed to unnecessarily complicate the dimmer module's layout.
It should therefore be appreciated that there is a need for an improved dimmer module layout that obviates the need for unnecessary electrical conductors for conveying control signals and electrical power from one component to another, yet that retains the benefits of a plug-in assembly. The present invention fulfills that need.